Reference is made to FIGS. 1 to 2, FIG. 1 is a schematic view showing the structure of a typical electronic expansion valve, and FIG. 2 is a schematic view showing the structure of cooperation between a valve seat and a valve rod in FIG. 1.
The electronic expansion valve includes a valve house 100 and a valve seat component 10, a valve cavity is formed by arranging the valve house 100 and the valve seat component 10, and a valve rod 204 is provided inside the valve cavity. An electric machine 104 and a gear system 106 are provided inside the valve house 100, the electric machine 104 drives the gear system 106 to rotate, and the gear system 106 cooperates with the valve rod 204 to drive the valve rod 204 to move upward and downward along an axial direction.
A valve port 202, a first connecting port 34 and a second connecting port 36 are provided in the valve seat component 10, and the valve port 202 opens or closes to allow or prevent the communication between the first connecting port 34 and the second connecting port 36. Referring to FIG. 1, a valve rod cone-shaped end 42 is arranged at a lower end of the valve rod 204, and the communication between the first connecting port 34 and the second connecting port 36 is disconnected when the valve rod 204 moves downward to block the valve port 202. The communication between the first connecting port 34 and the second connecting port 36 is allowed when the valve rod moves upward to leave the valve port 202.
The valve rod 204 is generally machined to form a structure having a small upper end and a large lower end, for ensuring that the valve rod 204 of such structure can be assembled, the valve seat component 10 is a separated structure, which includes a valve seat base 102 and a valve seat sleeve 16. An axial through-hole is provided in the valve seat sleeve 16, thus the valve rod 204 can move axially inside the axial through-hole. A lower end of the valve seat sleeve 16 presses against an upper end of the valve seat base 102; to ensure a reliable connection between the valve seat sleeve 16 and the valve seat base 102, a positioning sleeve 20 is further provided, and the positioning sleeve 20 is sleeved on a portion where the valve seat sleeve 16 presses against the valve seat base 102.
For improving the performance of the electronic expansion valve, a lateral hole 205 is provided in the valve rod 204, as shown in FIG. 2. When the lateral hole 205 is arranged above, namely the lateral hole 205 is arranged at an upper side of the valve rod cone-shaped end 42, in this case if a high-pressure refrigerant enters via the second connecting port 36, the valve port 202 is easy to open while not easy to close; if the high-pressure refrigerant enters via the first connecting port 34, the valve port 202 is easy to close but not easy to open. When the lateral hole 205 is arranged below, the open and closed conditions of the valve port are opposite to the above case. Therefore, for the valve of the electronic expansion valve with such a structure, the resistances to open valve when the refrigerant enters via the first connecting port and the second connecting port respectively are unequal and are difficult to balance.
Moreover, in order to assemble the valve rod 204, the valve seat component 10 needs to be designed as a separated structure, the separated structure is complicated, the assembled valve seat component is apt to loose due to transportation vibration or the effect of vibration of device, which may result in an outleakage of the refrigerant inside the valve, thereby causing refrigeration failures and environmental pollutions. Therefore, a bowl-shaped plastic sheet 104 is provided for sealing, as shown in FIG. 1, the bowl-shaped plastic sheet 104 is arranged around the valve rod 204, and has an opening facing a direction of the valve housing 100.
However, the bowl-shaped plastic sheet 104 can only realize a one-way seal when the high-pressure refrigerant enters via the opening (namely the high-pressure refrigerant enters via the first connecting port 34), if the high-pressure refrigerant enters via a port opposite to the opening (that is the high-pressure refrigerant enters via the second connecting port 36), the bowl-shaped plastic sheet 104 is shrunken under the action of force, thus still causing refrigerant leakage.
In view of this, a technical issue to be addressed urgently by those skilled in the field is to improve the structure of the electronic expansion valve to balance the capacities to open and close the valve.